That lot has certainly been lacking a bit of love, but it all looks like standard stuff. I'd start at the back, dissamble the whole lot and rebuild with stainless components wherever possible. As Sewin says, there are plenty of exhaust specialists out there. If it was me, I'd go to Merlin Motorsport because they are quite close and do a huge range of bits.
https://www.merlinmotorsport.co.uk/...ts/2-inch-diameter/stainless-steel-parts
